Self-centering hole locater



3, 19 10 D. s. HEETER' 3,492,134

SELF-CENTERING HOLE LOCATER Filed Oct. 23. 1967 FIGZ INVENTOR DWIGHT S. HEETER ATTORNEYS United States Patent Oflice 3,492,734 Patented Feb. 3, 1970 ABSTRACT OF THE DISCLOSURE A self-centering hole locater and punch formed of a barrel slidably receiving a downwardly extending axially bored piston connected to a tube extending upwardly through the barrel, and a free, axially slidable punch stern extending through and in face to face contact with the tube wall and the piston bore for lateral support against buckling and for tree removal therefrom.

BACKGROUND OF INVENTION In shop practices, such as in tool and die construction work, it frequently becomes necessary to drill a hole in a workpiece, which hole is accurately and concentrically aligned with an existing hole in a different workpiece. For example, in fastening together a pair of plates, one of which already has a hole drilled through it, it is necessary to drill a hole in the second of the two plates, but in accurate alignment with the first hole.

Locating and accurately marking the center of the existing hole upon the non-drilled workpiece, particularly where accuracy is required, has always been a difiicult problem for the shop workers.

Although various prior art types of devices have been constructed for this purpose, these uniformly lack accuracy and more importantly, have been complicated, expensive and easily broken in use. This is particularly applicable to the prior art attempts to use a straight stem, guided in some way by a supporting structure, wherein by tapping the upper end of the stem, the lower end forms a mark upon the non-drilled workpiece. Here, the life and accuracy of the stems have been particularly short and these have tended to buckle or bend out of shape when tapped at their upper end with sufficient force to form a mark upon a piece of metal.

SUMMARY OF INVENTION Hence, it is an object of this invention, to provide a marking stem whose upper end may be tapped and whose lower end is guided in such a way as to be accurately aligned along the central axis of an already drilled hole, with the stem completely supported and guided substantially throughout its length so that it will accurately follow said center line Without buckling or breaking.

A further object of this invention is to provide a tool formed of a few simply constructed and easily disassembleable parts, including a piston snugly but slidably fitted within the bore of a barrel and connected at its upper end to an elongated screw which extends through the barrel with the stem snugly fitted through the length of the screw and piston for slidable movement relative thereto, with the lower end of the piston being shaped to center within a hole, that is being conically formed, and with the barrel being movable against a spring force, to firmly seat against the already drilled workpiece to thereby guide the stem and closely support it against buckling or bending when the upper end of the stem is tapped in order to cause the lower end to form a mark upon a piece of metal located below the already drilled hole.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS FIG. 1 illustrates in cross-section the five separate parts which make up the hole locater herein, the parts being shown in disassembled relationship.

FIG. 2 is an elevational view of the hole locater in normal position.

FIG. 3 is an elevational, cross-sectional view similar to FIG. 2, and

FIG. 4 is an elevational view showing the hole locater as actually used in marking the center of a hole upon a workpiece.

DETAILED DESCRIPTION The self-centering hole locater 10 comprises a cylindrically shaped barrel having a surrounding, knurled, grip portion 12. As shown in FIG. 1, a central bore 13 is formed in the barrel, extending from the lower edge of the barrel to a point slightly beneath the upper edge of the barrel to thereby form a closed upper end 14 having a coaxially arranged, smaller diameter opening 15 formed therein. The lower edge of the barrel forms an annulus or guide surface arranged in a plane which is perpendicular to the axis of the barrel.

A cylindrically shaped piston 16 is snugly, but slidably fitted within the bore, with approximately half of the piston being arranged within the barrel with the remainder extending downwardly below the lower edge of the barrel.

The upper end of the piston is formed with a drilled socket 17 to receive the lower end of a coil spring 18 which is arranged within the bore so that its upper end presses against the lower surface of the closed portion 14 of the barrel.

Beneath the socket 17 is a threaded opening or lower socket 19 which threadedly receive and engages with the threaded lower end 20 of an elongated, uniform diameter screw 21 having a knurled head 22 which normally (see FIG. 2) rests against the upper end of the barrel. An axially concentric opening 23 extends through the entire length of the screw and communicates with a second opening 24, of the same diameter, formed through the piston 16.

An elongated, straight stem 25, formed of a hardened metal, is snugly, but slidably fitted through the aligned openings 23 and 24 to thereby extend above the screw head 22 and below the piston 16. The lower end of the piston is formed in a conically shaped or tapered configuration 27 with the lower end 26 of the stem 25 being similarly shaped to thus form a complete conical surface with the lower end of the piston (see FIG. 2).

As illustrated in FIG. 1, the entire device is made of only five, relatively simple parts which are easily assembled and disassembled merely by connecting or disconnecting the screw 21 from the piston 16. At the same time, substantially all of the stem, particularly its middle portion is closely guided and held to prevent its buckling under impact while at the same time the stem, being unrestrained, can be easily removed when needed, either for replacement or repair, or separate use as a scriber.

OPERATION In operation, the parts are assembled together as illustrated in FIGS. 2 and 3. Thereafter, the user, having a workpiece 30, such as a fiat plate, with a hole 31 drilled in the workpiece and with the hole being perpendicular with the surfaces of the workpiece, positions the workpiece upon a separate surface 32 upon which a mark is to be made to indicate the center of the hole 31. For example, the surface 32 may be part of a second workpiece 33 which is also to be drilled with a hole accurately corresponding to the already drilled hole 31 for receiving an accurately aligned fastener.

The user first positions the tapered or conically shaped lower end 27 in the hole 31 so that it partially fits within the hole. For this purpose, the hole, must, of course, be of smaller diameter than the piston. Thereafter, the user, gripping the knurled portion 12, pushes the barrel 11 towards the workpiece 30 so that the lower edge of the barrel firmly seats or abuts the workpiece surface. In that manner, the stem 25 is accurately aligned coaxially with the center of the hole 31. The stem is then moved downwardly until its point 26 contacts the surface 32 and by tapping the upper end of the stem with a suitable hammer or mallet, a mark is made to thereby locate a drill to be used to make the corresponding hole in the workpiece 33.

This invention may be further developed within the scope of the following claim. Accordingly, it is desired that the foregoing description be read as being merely illustrative of an operative embodiment of this invention, and not in a strictly limited sense.

Having fully described an operative embodiment of this invention, I now claim:

1. In a self-centering hole locater-punch formed of a normally vertical tubular barrel having a closed upper end formed with a central opening, with an elongated axially bored piston axially slidably fitted within and extending beneath the lower end of the barrel and having a conically tapered lower end,

and a vertically elongated uniform diameter tube releasably secured to the upper end of the piston and axially slidably extending through said opening, the tube having a head formed on its upper end normally engaging the top of the barrel;

and a coil spring surrounding the tube and abutting the barrel and piston upper ends;

a thin, straight, elongated punch stem extending through and above the tube and through and below the piston bore;

the improvement comprising:

the portion of said stem arranged within the tube and bore being at all times in full face to face contact with the tube wall and the wall of the bore for full lateral support against buckling, and the stern being free of securernent and otherwise unrestrained for free endwise movement within and removal from the tube and bore.

References Cited UNITED STATES PATENTS 1,225,191 5/1917 Throckmorton 33191 1,225,265 5/1917 Miller 33191 2,595,347 6/1952 Flemming 33191 WILLIAM D. MARTIN JR., Primary Examiner 

